Many mechanisms require a form of rotary drive for operation, such as some valves, for example ball valves. Many drive or actuator systems exist which are capable of generating a rotary drive force or torque to be applied to a mechanism. For example, it is known to utilise a linear actuator, such as a linear piston, in combination with a suitable movement translator, such as a crank system, to convert the linear movement to rotation. However, the requirement for a suitable movement translator may add to the complexity of the actuator, with the added potential for failure.
It is known in the art to utilise direct rotary drive systems, such as rotary pistons, to provide a rotary drive force. However, such systems may include complexities of maintaining internal sealing during operation.